1. Field of the Invention
The present invention relates to an actuator, and more particularly, to a pneumatic actuator.
2. Statement of the Problem
An actuator is a device that performs some mechanical action. One actuator is a piston, wherein a plunger of the piston moves in a reciprocating manner. The plunger can therefore be connected to some manner of work piece or other mechanical system.
In some actuator applications, it is desirable to have more than one actuation speed and/or more than one actuation force over the range of motion of the actuator. For example, in a spot welder machine, a pair of welding jaws must be brought together onto a work piece during a welding operation. The jaws must clamp onto the work piece with a desired force. Therefore, at the end of a clamping motion range, a relatively high actuation force must be provided to the welding jaws. However, an actuator that provides a high level of force typically provides a relatively small range of actuation travel. This can be a problem where the jaws of the spot welder machine must open wide in order to be positioned on the work piece. Therefore, a jaw actuator of the spot welder machine needs to move relatively rapidly during a first actuation span and a large force is not required. During the second actuation span, the jaws need to move only a small distance, but must be able to provide a large clamping force.